Reprocessing of polymeric compositions

ABSTRACT

A method may include reprocessing a polymer composition comprising a crosslinked polymeric composition, wherein the crosslinked polymeric composition comprises a matrix polymer having a polar polymer internal phase that is selectively crosslinked with a crosslinking agent, wherein the reprocessed polymer composition retains an environmental stress cracking resistance within 60% of the value for the initial polymer composition when measured according to ASTM D-1693 procedure B and wherein the reprocessed polymer composition presents a Normalized Property Balance Index (N PBI ) greater than about 1.0.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of PCT/IB2019/020011filed on Apr. 19, 2019, which claims priority to U.S. Provisional PatentApplication No. 62/678,833 filed on May 31, 2018, and this applicationis a continuation-in-part application of U.S. patent application Ser.No. 15/282,169 filed on Sep. 30, 2016, which claims priority to U.S.Provisional Patent Application No. 62/236,042 filed on Oct. 1, 2015, allof which are incorporated herein by reference.

BACKGROUND

Polyolefins such as polyethylene (PE) and polypropylene (PP) may be usedto manufacture a varied range of articles, including films, moldedproducts, foams, and the like. Polyolefins may have characteristics suchas high processability, low production cost, flexibility, low densityand recycling possibility. However, physical and chemical properties ofpolyolefin compositions may exhibit varied responses depending on anumber of factors such as molecular weight, distribution of molecularweights, content and distribution of comonomer (or comonomers), methodof processing, and the like.

Methods of manufacturing may utilize polyolefin's limited inter- andintra-molecular interactions, capitalizing on the high degree of freedomin the polymer to form different microstructures, and to modify thepolymer to provide varied uses in a number of technical markets.However, polyolefin materials may have a number of limitations, whichcan restrict application such as susceptibility to deformation anddegradation in the presence of some chemical agents, and low barrierproperties to various gases and a number of volatile organic compounds(VOC). Property limitations may hinder the use of polyolefin materialsin the production of articles requiring low permeability to gases andsolvents, such as packaging for food products, chemicals, householdchemicals, agrochemicals, fuel tanks, water and gas pipes, andgeomembranes, for example.

While polyolefins are utilized in industrial applications because offavorable characteristics such as high processability, low productioncost, flexibility, low density, and ease of recycling, polyolefincompositions may have physical limitations, such as susceptibility toenvironmental stress cracking (ESC) and accelerated slow crack growth(SCG), which may occur below the yield strength limit of the materialwhen subjected to long-term mechanical stress. Polyolefin materials mayalso exhibit sensitivity to certain groups of chemical substances, whichcan lead to deformation and degradation. As a result, chemicalsensitivities and physical limitations may limit the success in thereplacement of other industry standard materials, such as steel andglass, with polyolefin materials because the material durability isinsufficient to prevent chemical damage and spillage.

Conventionally, methods of altering the chemical nature of the polymercomposition may include modifying the polymer synthesis technique or theinclusion of one or more comonomers. However, modifying the polyolefinmay also result in undesirable side effects. By way of illustration,increasing the molecular weight of a polyolefin may produce changes inthe SCG and ESC, but can also increase viscosity, which may limit theprocessability and moldability of the polymer composition.

Other strategies may include inclusion of a comonomer and/or blendingpolyolefins with other polymer classes and additives to confer variousphysical and chemical attributes. For example, polyolefins may becopolymerized with alpha-olefins having a lower elastic modulus, whichresults in a considerable increase in environmental stress crackingresistance (ESCR) and resistance to impact but adversely affects thestiffness of the polymer. However, the use of alpha-olefins may havelimited effectiveness because, while the incorporation of alpha-olefincomonomers must occur in the high molecular weight fraction in order toaffect ESC and impact resistance, many popular catalyst systems have alow probability of inserting alpha-olefins in the high molecular weightfraction, an important factor in forming “tie molecules” between thechains of the surrounding polyolefin that are responsible fortransferring stress between the crystalline regions and, consequently,responsible for important mechanical properties. The result is theproduction of a polymer composition having reduced structural stiffness.It is also noted that, while advances have developed catalysts thatincrease the likelihood of displacing the incorporation of a comonomerto the highest molecular weight range, and that multiple reactors may beused to address these limitations, such modifications are expensivealternatives and not wholly effective in balancing resistance to impactand ESC without negatively affecting stiffness.

Polymer modification by blending may vary the chemical nature of thecomposition, resulting in changes to the overall physical properties ofthe material. Material changes introduced by polymer blending may beunpredictable, however, and, depending on the nature of the polymers andadditives incorporated, the resulting changes may be uneven and somematerial attributes may be enhanced while others exhibit notabledeficits. The incorporation of a second phase into the matrix polymer,which generally has a different chemical nature, may increase theresistance to impact and ESC resistance in some cases. However, like thecopolymerization strategy, polymer blends are often accompanied by amarked loss in stiffness, because the blended materials may have lowerelastic modulus than the matrix polyolefin.

Accordingly, there exists a continuing need for developments inpolyolefin compositions to have increases in environmental stresscracking resistance while balancing the mechanical properties of thepolymer.

SUMMARY

This summary is provided to introduce a selection of concepts that arefurther described below in the detailed description. This summary is notintended to identify key or essential features of the claimed subjectmatter, nor is it intended to be used as an aid in limiting the scope ofthe claimed subject matter.

In one aspect, embodiments disclosed herein relate to a method thatincludes reprocessing a polymer composition comprising a crosslinkedpolymeric composition, wherein the crosslinked polymeric compositioncomprises a matrix polymer having a polar polymer internal phase that isselectively crosslinked with a crosslinking agent, wherein thereprocessed polymer composition retains an environmental stress crackingresistance within 60% of the value for the initial polymer compositionwhen measured according to ASTM D-1693 procedure B and wherein thereprocessed polymer composition presents a Normalized Property BalanceIndex (N_(PBI)) greater than about 1.0, wherein the N_(PBI) iscalculated according to the formula:

${N_{PBI} = \frac{{PBI}_{sample}}{{PBI}_{reference}}},$

where PBI_(Sample) is the property balance index for a sample of thepolymer composition, and PBI_(Reference) is the property balance indexof a reference polymer composition consisting of a matrix polymercomposition without the reprocessing; and wherein PBI is calculatedaccording to the formula:

${{PBI} = \frac{F\; M \times {IR} \times {ESCR}}{10^{7}}},$

where FM is the stiffness of the sample as determined by secant modulusof elasticity at 1% deformation according to ASTM D-790, IR is the IZODimpact resistance according to ASTM D-256, and ESCR is the environmentalstress cracking resistance according to ASTM D1693 procedure B.

In another aspect, embodiments disclosed herein relate to a polymercomposition that includes a crosslinked polymeric compositioncomprising: a matrix polymer comprising a polyolefin, and one or morepolymer particles dispersed in the polymer matrix, wherein the one ormore polymer particles comprise a polar polymer selectively crosslinkedwith a crosslinking agent, wherein the crosslinked polymer compositionretains an environmental stress cracking resistance after reprocessingthat is within 60% of the value for the initial crosslinked polymericcomposition when measured according to ASTM D-1693 procedure B.

In yet another aspect, embodiments disclosed herein relate to amanufactured article that includes a polymer composition that includes acrosslinked polymeric composition comprising: a matrix polymercomprising a polyolefin, and one or more polymer particles dispersed inthe polymer matrix, wherein the one or more polymer particles comprise apolar polymer selectively crosslinked with a crosslinking agent, whereinthe crosslinked polymer composition retains an environmental stresscracking resistance after reprocessing that is within 60% of the valuefor the initial crosslinked polymeric composition when measuredaccording to ASTM D-1693 procedure B.

In yet another aspect, embodiments disclosed herein relate to use of arecycled crosslinked polymer composition to improve the properties of asecond polymer composition, the recycled crosslinked polymer compositioncomprising a matrix polymer having a polar polymer internal phase thatis selectively crosslinked with a crosslinking agent.

In yet another aspect, embodiments disclosed herein relate to use of arecycled crosslinked polymer composition to form an injection moldedarticle, a thermoformed article, a film, a foam, a blow molded article,a 3D printed article, a compression molded article, a coextrudedarticle, a laminated article, an injection blow molded article, arotomolded article, an extruded article, or a pultruded article, whereinthe recycled crosslinked polymer composition comprising a matrix polymerhaving a polar polymer internal phase that is selectively crosslinkedwith a crosslinking agent.

Other aspects and advantages of the claimed subject matter will beapparent from the following description and the appended claims.

DETAILED DESCRIPTION

Embodiments of the present disclosure are directed to polymercompositions that contained a crosslinked polymeric composition that maybe used to maintain the properties (including but not limited toenvironmental stress cracking resistance) during reprocessing thereof,as well as during reprocessing of a secondary polymer composition towhich the crosslinked polymeric composition is added. The crosslinkedpolymeric composition may include a matrix polymer of a polyolefin andone or more polymer particles dispersed in the polymer matrix, where oneor more polymer particles includes a polar polymer that is selectivelycrosslinked with a crosslinking agent. In particular, the crosslinkedpolymeric composition may provide function to improve the properties ofthe secondary polymer composition to which the crosslinked polymericcomposition is added. The crosslinked polymer composition containing amixture of polyolefin and polar polymer particles that may inducestructural and/or morphological changes when compared to an unmodifiedpolymer or blend, which may provide for the property improvement duringreprocessing particularly as compared to a matrix polymer alone (withoutthe selectively crosslinked particles) that is subjected to suchreprocessing and/or a secondary polymer composition that is reprocessed.

In some embodiments, the polar polymer within the polymer compositionmay be crosslinked by a crosslinking agent to generate particulatescontaining intra-particle covalent linkages between the constituentpolar polymer chains. Depending on the concentration and relativeproximity of adjacent polar polymer particles, inter-particle covalentlinkages may also be formed. The crosslinked polar polymer particles maycreate changes in the physical and physicochemical properties, includingincreases in ESCR, and improvement in the balance of stiffness/impactresistance mechanical properties in relation to the properties of pure(unmodified or blended) polyolefins, as well as to secondary polymercompositions to which the crosslinked polymeric was added. The presentinventors have found that such properties survive reprocessing of thepolymer composition such that the polymer composition can be reprocessedwithout substantial losses in its properties, or with a slow decay inits properties.

In one or more embodiments, the balance of properties for modifiedpolymer compositions may be expressed through a property balance index,which considers the combination of the flexural modulus, impactresistance and ESCR, discussed in greater detail below. The propertybalance index may be normalized against a reference polyolefin (withoutthe polar polymer, etc.), and advantageously, the polymer compositionsof the present disclosure may achieve a normalized property balanceindex that ranges from about 1.5 to 10, or greater than 1.5, or greaterthan 1.8, or from 3 to 6 in more particular embodiments.

Crosslinked Polymeric Compositions

In one or more embodiments, polymer compositions in accordance with thepresent disclosure may include a polyolefin matrix polymer having andinternal polar polymer phase that is crosslinked by a suitablecrosslinking agent. Crosslinked polymeric compositions may be blendedwith various polymer types to modify a number of properties includingenvironmental stress cracking resistance, and the like.

Matrix Polymer

Crosslinked polymeric compositions in accordance with the presentdisclosure may include a matrix polymer component that surrounds othercomponents in the composition, including polar polymer particles andother additives. In one or more embodiments, matrix polymers may includepolyolefins produced from unsaturated monomers with the general chemicalformula of C_(n)H_(2n). In some embodiments, polyolefins may includeethylene homopolymers, copolymers of ethylene and one or more C3-C20alpha-olefins, propylene homopolymers, heterophasic propylene polymers,copolymers of propylene and one or more comonomers selected fromethylene and C4-C20 alpha-olefins, olefin terpolymers and higher orderpolymers, and blends obtained from the mixture of one or more of thesepolymers and/or copolymers.

In one or more embodiments, matrix polymer may be selected frompolyethylene with a density ranging from a lower limit selected from oneof 0.890, 0.900, 0.910, 0.920, 0.930 and 0.940 g/cm³ to an upper limitselected from one of 0.945, 0.950, 0.960 and 0.970 g/cm³ measuredaccording to ASTM D792, a melt index (I₂) ranging from a lower limitselected from one of 0.01, 0.1, 1, 10 and 50 g/10 min to an upperlimitselected from one of 10, 20, 50, 60, 100, and 200 g/10 min according toASTM D1238 at 190° C./2.16 kg and/or a melt index (I₂₁) ranging from alower limit selected from one of 0.1, 1, 3. 5 10 and 50 g/10 min to anupper limit selected from one of 10, 20, 30, 50, 100, 500, and 1000 g/10min according to ASTM D1238 at 190° C./21.6 kg.

In one or more embodiments, the matrix polymer may include a highdensity polyethylene, with a density ranging from 0.930 g/cm³ to 0.970g/cm³ according to ASTM D792 and a High Load Melt Index (HLMI) rangingfrom 1 to 60 g/10 min according to ASTM D1238 at 190° C./21.6 kg. In oneor more embodiments, the matrix polymer may include a high densitypolyethylene, with a density ranging from 0.940 g/cm³ to 0.970 g/cm³according to ASTM D792 and a High Load Melt Index (HLMI) ranging from 1to 60 g/10 min according to ASTM D1238 at 190° C./21.6 kg.

In one or more embodiments, polymer compositions may contain a percentby weight of the total composition (wt %) of matrix polymer ranging froma lower limit selected from one of 30 wt %, 40 wt %, 50 wt %, 60 wt %,75 wt %, and 85 wt %, to an upper limit selected from one of 60 wt %, 75wt %, 80 wt %, 90 wt %, 95 wt %, 99.5 wt % and 99.9 wt %, where anylower limit can be used with any upper limit.

Polar Polymers

Polymer compositions in accordance with the present disclosure mayinclude one or more polar polymers that are combined with a polyolefinand, further, may be crosslinked by one or more crosslinking agents. Asused herein, a “polar polymer” is understood to mean any polymercontaining hydroxyl, carboxylic acid, carboxylate, ester, ether,acetate, amide, amine, epoxy, imide, imine, sulfone, phosphone, andtheir derivatives, as functional groups, among others. The polar polymermay be selectively crosslinked by an appropriate crosslinking agent,where the selective crosslinking may occur between the functional groupsby reacting with a suitable crosslinking agent in the presence ofpolyolefins, additives, and other materials. Thus, the crosslinkingagent is selected to react with the polar polymer but without exhibitingreactivity (or having minimal reactivity towards) the polyolefin. Insome embodiments, polar polymers include polyvinyl alcohol (PVOH),ethylene vinyl alcohol (EVOH) copolymer, ethylene vinyl acetatecopolymer (EVA) and mixtures thereof. In particular embodiments, polarpolymers include polyvinyl alcohol.

One or more polar polymers in accordance with the present disclosure maybe produced by hydrolyzing a polyvinyl ester to produce free hydroxylgroups on the polymer backbone. By way of example, polar polymersproduced through hydrolysis may include polyvinyl alcohol generated fromthe hydrolysis of polyvinyl acetate. The degree of hydrolysis for apolymer hydrolyzed to produce a polar polymer may be within the range of30% and 100% in some embodiments, and between 70% and 99% in someembodiments.

Polar polymers in accordance with the present disclosure may have anintrinsic viscosity in the range of 2 mPa·s to 110 mPa·s in someembodiments, and between 4 mPa·s and 31 mPa·s in some embodiments.Intrinsic viscosity may be measured according to DIN 53015 using a 4%aqueous solution at 20° C.

In one or more embodiments, polar polymer in accordance with the presentdisclosure may form a distinct phase within the polymer composition,which may be in the form of particles having an average particle size ofless than 200 μm. Particle size determinations may be made in someembodiments using SEM techniques after the combination with thepolyolefin. Polar polymer particles in accordance with the presentdisclosure may have an average particle size having a lower limitselected from 0.01 μm, 0.5 μm, 1 μm, and 5 μm, and an upper limitselected from 10 μm, 20 μm, 30 μm, 50 μm, and 200 μm, where any lowerlimit may be used with any upper limit.

Particle size may be determined by calculating relevant statistical dataregarding particle size. In some embodiments, SEM imaging may be used tocalculate particle size and develop size ranges using statisticalanalysis known for polymers and blends. Samples may be examined usingSEM after hot pressing the samples in accordance with ASTM D-4703 andpolishing the internal part of the plate by cryo-ultramicrotomy. Samplesmay be dried and submitted to metallization with gold. The images may beobtained by FESEM (Field Emission Scanning Electron Microscopy, ModelInspect F50, from FEI), or by Tabletop SEM (Model TM-1000, fromHitachi). The size of each crosslinked polar polymer particle may bemeasured from these images using the software LAS (version 43, fromLeica). Calibration may be performed using the scale bar of each imageand the measured values can be statistically analyzed by the software.The average value and standard deviation are given by the measurementof, at least, 300 particles.

In one or more embodiments, polymer compositions may contain a percentby weight of the total composition (wt %) of polar polymer ranging froma lower limit selected from one of 0.1 wt %, 0.25 wt %, 0.5 wt %, 1 wt%, 2 wt %, 5 wt %, 10 wt %, 15 wt %, and 25 wt %, to an upper limitselected from one of 5 wt %, 10 wt %, 15 wt %, 25 wt %, 50 wt %, 60 wt%, and 70 wt %, where any lower limit can be used with any upper limit.

Functionalized Polyolefin

In some embodiments, compatibilizing agents such as functionalizedpolyolefins may be optionally added to modify the interactions betweenthe polyolefin and the polar polymer. As used herein, “functionalizedpolyolefin” (or compatibilizing agent) is understood to mean anypolyolefin which had its chemical composition altered by grafting orcopolymerization, or other chemical process, using polar functionalizingreagents. Functionalized polyolefins in accordance with the presentdisclosure include polyolefins functionalized with maleic anhydride,maleic acid, acrylic acid, methacrylic acid, itaconic acid, itaconicanhydride, methacrylate, acrylate, epoxy, silane, succinic acid,succinic anhydride, ionomers, and their derivatives, or any other polarcomonomer, and mixtures thereof, produced in a reactor or by grafting.

In one or more embodiments, polymer compositions may contain a percentby weight of the total composition (wt %) of functionalized polyolefinranging from a lower limit selected from one of 0.1 wt %, 0.5 wt %, 1 wt%, and 5 wt %, to an upper limit selected from one of 5 wt %, 7.5 wt %,10 wt %, and 15 wt %, where any lower limit can be used with any upperlimit.

Crosslinking Agent

In one or more embodiments, a crosslinking agent may be used tocrosslink a selected polymer phase in a polymer composition. As usedherein, a “crosslinking agent” is understood to mean any bi- ormulti-functional chemical substance capable of reacting selectively withthe polar groups of a polymer, forming crosslinks between and within theconstituent polymer chains. As used herein, “selective” or “selectively”used alone or in conjunction with “crosslinking” or “crosslinked” isused to specify that the crosslinking agent reacts exclusively with thepolar polymer, or that the crosslinking agent reacts with the polarpolymer to a substantially greater degree (98% or greater, for example)than with respect to the polyolefin polymer.

Crosslinking agents in accordance with the present disclosure may reactpreferentially with a polar polymer, and may be non-reactive (orsubstantially non-reactive) with polyolefin. The crosslinking agent isconsidered non-reactive (or not substantially reactive) to polyolefinwhen a composition consisting of the crosslinking agent and polyolefinmay be processed with no changes or variations within a value of 2% (orlower) in rheology (complex viscosity), FTIR, and ESCR according to anyapplicable measurement method, as compared to a composition containingthe polyolefin alone, according to any applicable measurement methodprovided the same method is applied to the comparative polyolefin and tothe composition consisting of polyolefin and crosslinking agent.

In one or more embodiments, crosslinking agents in accordance with thepresent disclosure may include linear, branched, saturated, andunsaturated carbon chains containing functional groups that react withcounterpart functional groups present on the backbone and termini of apolar polymer incorporated into a polymer composition. In someembodiments, crosslinking agents may be added to a pre-mixed polymerblend containing a polyolefin and polar polymer particles, in order tocrosslink the polar polymer in the presence of the polyolefin. Followingaddition to the pre-mixed polymer blend, a crosslinking agent may reactwith the polar polymer within the particles, creating intraparticlecrosslinks between the polar polymer chains. Crosslinking agents inaccordance with the present disclosure may include, for example, maleicanhydride, maleic acid, itaconic acid, itaconic anhydride, succinicacid, succinic anhydride, succinic aldehyde, adipic acid, adipicanhydride, phthalic anhydride, pthalic acid, citric acid, glutaconicacid, glutaconic anhydride, glutaraldehyde, sodium tetraborate, organictitanates such as tetrabutyl titanate, organic zirconates such aszirconium(IV) bis(diethyl citrato)dipropoxide, methoxy polyethyleneglycol acrylates, ethoxy polyethylene glycol acrylates, ethylene glycoldiacrylate, ethylene glycol dimethacrylate, polypropylene glycoldiacrylate, polypropylene glycol dimethacrylate, 1,3-butylene glycoldiacrylate, 1,3-butylene glycol dimethacrylate, neopentyl glycoldiacrylate, neopentyl glycol dimethacrylate, trimethylol ethanetriacrylate, trimethylol ethane trimethacrylate, trimethylol propanetriacrylate, trimethylol propane trimethacrylate, and tetramethylolmethane tetracrylate, their derivatives and mixtures thereof.

In one or more embodiments, crosslinking agents may be added to a blendused to form a polymer composition at a percent by weight (wt %) of theblend ranging from a lower limit selected from one of 0.001 wt %, 0.01wt %, 0.05 wt %, 0.5 wt %, 1 wt %, and 2 wt % to an upper limit selectedfrom one of 1.5 wt %, 2 wt %, 5 wt %, and 10 wt %, where any lower limitcan be used with any upper limit.

As described herein, the crosslinked polymer composition may bereprocessed without substantial (or slow) decay in the environmentalstress cracking resistance, as well as a Normalized Property BalanceIndex (N_(PBI)). Reprocessing may include regrinding the crosslinkedpolymer composition. Thus, a regrind is material that has undergone atleast one processing method such as molding or extrusion and thesubsequent sprue, runners, flash, rejected parts etc. are ground orchopped. For example, in extrusion blow molding, an amount of burr(often ranging from 10 to 30 wt % so as to maintain desired propertiesas much as possible) is produced, ground (known as regrind) andreprocessed for blending with virgin pellets. Both the heat history ofprocessing and the grinding may generally lead to degraded physical,chemical and flow properties for the resin and subsequent parts madefrom this regrind; however, in accordance with the present embodiments,the crosslinked polymeric composition of the present disclosure may bereground without substantial decay in one or more of the propertiesthereof. In accordance with one or more embodiments of the presentdisclosure, a crosslinked polymeric composition may be reprocessed alone(100% reprocessed resin) or in combination with a virgin resin,including at amounts that are as low as 10 to 99 wt %; however, it isunderstood that final polymer composition and article that is formed hasbetter properties, as described below, than comparative regrind withoutthe selectively crosslinked polar polymer particles.

Specifically, the loss of the stress cracking resistance duringreprocessing is low and the stress cracking resistance is very highcompared to the matrix polymer without the reprocessing. In one or moreembodiments, the crosslinked polymer composition retains anenvironmental stress cracking resistance after reprocessing that iswithin 60%, 70%, 80%, or even 90% in some embodiments of the value forthe initial crosslinked polymeric composition (prior to thereprocessing) when measured according to ASTM D-1693 procedure B. Inparticular, in one or more embodiments, the crosslinked polymericcomposition retains an environmental stress cracking resistance afterreprocessing at least 3 times, or at least 5 times, that is within 60%of the value for the initial crosslinked polymeric composition whenmeasured according to ASTM D1693 procedure B.

Changes in physical and chemical properties of polymer compositions inaccordance with the present disclosure are characterized using an indexof properties that may be used to quantify the changes in a respectivepolymer composition based on a balance of mechanical and ESCRproperties. Improvements in a material's flexural modulus, impactresistance and ESCR may translate to better performance in variousapplications. However, improvements in a single property may be offsetby losses in other properties. In order to quantify the overallimprovement of the material, the product of the individual properties ismonitored in the examples below. The “Property Balance Index” (PBI) isdefined as shown in Eq. 1 to quantify the property changes, wherein “FM”is the flexural modulus given by the secant modulus at 1% of deformationmeasured according to ASTM D-790 in MPa, “IR” is the IZOD impactresistance at 23° C. measured according to ASTM D-256 in J/m, and “ESCR”is the environmental stress cracking resistance measured according toASTM D-1693 procedure B in hours (h).

$\begin{matrix}{{PBI} = \frac{F\; M \times {IR} \times {ESCR}}{10^{7}}} & (1)\end{matrix}$

Definition of the Normalized Property Balance Index

To compare the magnitude of property changes for different polymersystems, the PBI values were normalized according to Eq. 2, whereN_(PBI) is the normalized property balance index calculated as:

$\begin{matrix}{N_{PBI} = \frac{{PBI}_{sample}}{{PBI}_{reference}}} & (2)\end{matrix}$

where PBI_(Sample) is the property balance index for a sample of thepolymer composition (reprocessed or not), and PBI_(Reference) is theproperty balance index of a reference polymer composition consisting ofa matrix polymer composition without the reprocessing.

Reprocessed polymer compositions in accordance with the presentdisclosure may exhibit an N_(PBI) higher than about 1.0 in someembodiments, or higher than about one of 1.5, 2.0, 3.0, 5.0, or 10 inother embodiments. In another embodiment, polymer compositions inaccordance with the present disclosure may exhibit an N_(PBI) fallingwithin the range of 1.5 to 10 in some embodiments, and within the rangeof 3 to 9 in some embodiments. Polymer compositions in accordance withthe present disclosure may exhibit an N_(PBI) that is at least 1.5 inother embodiments. In some embodiments, the N_(PBI) value may be atleast 1.8.

Secondary Polymer Compositions

Polymer compositions in accordance with the present disclosure mayinclude a mixture of crosslinked polymeric composition with a secondarypolymer composition. While a number of exemplary polymer materials aredescribed below it is envisioned that the secondary polymer compositionmay be any polymer suited for manufacturing applications.

In one or more embodiments, the secondary polymer compositions may beselected from polyolefin, polystyrene, polyamide, polyester, ethylenevinyl alcohol, polyacrylate, polymethacrylate, poly(vinyl chloride),polycarbonate, polysaccharides, and rubber. Specifically, in one or moreembodiments, the secondary polymer compositions may be selected frompolyethylene, polypropylene, polystyrene, poly(ethylene terephthalate),poly(vinyl chloride), polycarbonate, poly(methyl methacrylate) andnylon. Further, it is also envisioned that any of the secondary polymersmay be at least partially biobased. In one or more embodiments, thesecondary polymer composition (including any of the above) may be avirgin polymer resin, while in others embodiments, the secondary polymerresin is a post-industrial polymer resin (PIR), a post-consumer polymerresin (PCR), a regrind polymer resin or combinations thereof.

It is recognized that the recycling of polymeric materials is a majorconcern for the environment. Generally, the recycling of PCR resins isdifficult due to the degradation of the ESCR properties of the materialas compared to virgin resins, which limits possible end useapplications. It was surprisingly found that the addition of thecrosslinked polymeric composition as a masterbatch (MB) composition andeven in very low concentrations of MB, enables the increase in ESCRproperty of PIR and PCRs, making it possible to reuse them even inapplications that require high ESCR, which normally is impossible toachieve with recycled resins. In particular embodiments, PIRs, PCRs,regrind polymer resins and combinations thereof may be present in thepolymer composition in an amount higher than about 70 wt %, 80 wt %, 90wt %, 95 wt %, 96 wt %, 97 wt %, 98 wt % or 99 wt %.

In one or more embodiments, secondary polymer compositions may includehomopolymers, copolymers, graft copolymers, and heterophasic polymers.In some embodiments, secondary polymer compositions may includeacrylonitrile; butadiene-styrene (ABS); polyvinyl chloride (PVC);polyesters that include polylactic acid (PLA), polyglycolic acid (PGA),poly-co-lactic-glycolic acid (PLGA), and the like; polyamides thatinclude various nylons; polyacrylamide; polyacrylates;polymethacrylates; polyvinylalcohol (PVOH); polyolefins such aspolypropylene polymers and copolymers; high melt strength polyolefinsthat include branched polyolefins and crosslinked polyolefins;polyolefin copolymers such as ethylene vinyl acetate (EVA); heterophasicpolyolefins; polycarbonate (PC); polystyrene (PS); high impactpolystyrene (HIPS), polycaprolactone (PCL); and the like.

In one or more embodiments, secondary polymer may be selected frompolyethylene with a density ranging from a lower limit selected from oneof 0.890, 0.900, 0.910, 0.920, 0.930 and 0.940 g/cm³ to an upper limitselected from one of 0.945, 0.950, 0.960 and 0.970 g/cm³ measuredaccording to ASTM D792, wherein any lower limit may be used incombination with any upper limit, a melt index (I₂) ranging from a lowerlimit selected from one of 0.01, 0.1, 1, 10 and 50 g/10 min to an upperlimit selected from one of 10, 20, 50, 100, and 200 g/10 min accordingto ASTM D1238 at 190° C./2.16 kg, wherein any lower limit may be used incombination with any upper limit, and/or a melt index (I₂₁) ranging froma lower limit selected from one of 0.1, 1, 3. 5 10 and 50 g/10 min to anupper limit selected from one of 10, 20, 30, 50, 60, 100, 500, and 1000g/10 min according to ASTM D1238 at 190° C./21.6 kg, wherein any lowerlimit may be used in combination with any upper limit.

In one or more embodiments, the secondary polymer may include a highdensity polyethylene, with a density ranging from 0.930 g/cm³ to 0.970g/cm³ according to ASTM D792 and a High Load Melt Index (HLMI) rangingfrom 1 to 60 g/10 min according to ASTM D1238 at 190° C./21.6 kg.

In one or more embodiments, the secondary polymer may be present in thepolymer composition in an amount ranging from 5 to 99 wt % of thepolymer composition, including having a lower limit of 5, 10, 15, 20,25, 30, 35, 40, 45, or 50 wt % and an upper limit of 50, 55, 60, 65, 70,75, 80, 85, 90, 95, or 99 wt %, where any lower limit can be used withany upper limit.

Additives

In one or more embodiments, the polymer compositions of the presentdisclosure may contain a number of other functional additives thatmodify various properties of the composition such as antioxidants,pigments, fillers, reinforcements, adhesion-promoting agents, biocides,whitening agents, nucleating agents, anti-statics, anti-blocking agents,processing aids, flame-retardants, plasticizers, light stabilizers, andthe like.

Polymer compositions in accordance with the present disclosure mayinclude fillers and additives that modify various physical and chemicalproperties when added to the polymer composition during blending. In oneor more embodiments, fillers and nanofillers may be added to a polymercomposition to increase the barrier properties of the material byincreasing the tortuous path of the polymer matrix for the passage ofpermeate molecules. As used herein, “nanofiller” is defined as anyinorganic substance with at least a nanometric scale dimension. Polymercomposition in accordance with the present disclosure may be loaded witha filler and/or nanofiller that may include polyhedral oligomericsilsesquioxane (POSS), clays, nanoclays, silica particles, nanosilica,calcium nanocarbonate, metal oxide particles and nanoparticles,inorganic salt particles and nanoparticles, and mixtures thereof.

In one or more embodiments, fillers and/or nanofillers in accordancewith the present disclosure may be incorporated into a polymercomposition at a percent by weight (wt %) up to 70 wt %.

In one or more embodiments, polymer compositions may contain a percentby weight of the total composition (wt %) of one or more additivesranging from a lower limit selected from one of 0.001 wt %, 0.01 wt %,0.05 wt %, 0.5 wt %, and 1 wt %, to an upper limit selected from one of1.5 wt %, 2 wt %, 5 wt %, and 7 wt %, where any lower limit can be usedwith any upper limit.

Masterbatch Formulations

One or more of the wt % values mentioned above with respect to each ofthe components refer in fact to amounts that may be used to form such amasterbatch. In one or more embodiments, a masterbatch polymercomposition may contain a percent by weight of the total composition (wt%) of crosslinked polar polymer ranging from a lower limit selected fromone of 10 wt %, 20 wt % 25 wt %, 30 wt %, 40 wt %, and 50 wt % to anupper limit selected from one of 50 wt %, 60 wt %, and 70 wt %, whereany lower limit can be used with any upper limit. In particular, asdiscussed herein, the crosslinked polymeric composition may beformulated as a masterbatch formulation that is combined with asecondary polymer composition to improve the properties of the secondarypolymer composition, which may be a virgin polymer resin or a recycledmaterial (including post-industrial resins, post-consumer resins, andregrind polymer resin). Specifically, even for overly degraded recycledmaterials, the masterbatch formulation (crosslinked polymericcomposition) may be used to improve the properties of the secondarypolymer composition in order to recover or restore (at least partiallyor wholly) the properties of the secondary polymer composition to itsoriginal level (i.e., to a level that is close to or substantially thesame as a virgin resin thereof) or even higher than the original level.

As noted, in the masterbatch composition, the polymer compositioncontains concentrations of polar polymer that are high relative to thepolar polymer concentration in a final polymer blend for manufacture oruse. Thus, prior to use to form a manufactured article, the masterbatchcomposition may be combined with an additional quantity of polyolefin toarrive at a polar polymer concentration in the final composition that islower than the masterbatch concentration. For example, the crosslinkedpolymeric composition may be present in the final polymer composition(combined with the secondary polymer composition) at a percent by weightof the polymer composition that ranges from 0.01 wt % to 95 wt %, wherethe lower limit may include any of 0.01, 1, 5, 10, 15, 20, 25, 30, 35,40, 45, or 50 wt %, and the upper limit includes any of 50, 55, 60, 65,70 75, 80, 85, 90, or 95 wt %, where any lower limit can be used incombination with any upper limit.

Polymer Composition Preparation Methods

Polymer compositions in accordance with the present disclosure may beprepared by a number of possible polymer blending and formulationtechniques, which will be discussed in the following sections. Inparticular, as described herein, a crosslinked polymeric composition mayoptionally be combined with a secondary polymer composition; whereincombining the crosslinked polymeric composition with the secondarypolymer compositions improves the environmental stress crackingresistance of the polymer composition with respect to the secondarypolymer composition alone, particularly during reprocessing of thesecondary polymer composition. Further, it is also envisioned that thecrosslinked polymeric composition may be reprocessed and then added to asecondary polymer composition, i.e., the reprocessing of the secondarypolymeric composition is optional.

In one or more embodiments, the crosslinked polymeric composition iscombined with a secondary polymer composition in a melt blend process.In one or more other embodiments, the crosslinked polymeric compositionis combined with a secondary polymer composition in a dry blend process.Thus, the crosslinked polymeric may be formulated as a masterbatchformulation that may be diluted in a subsequent melt-blend or dry blendprocess to form the final polymer composition having the improvedproperties. For example, the crosslinked polymeric composition may beinitially formed, such as in a reactive extrusion process or the like toform the selectively crosslinked polymer particles within the matrixpolymer. Such crosslinked polymeric composition may subsequently becombined with a secondary polymer composition, may subjected to aconventional extrusion process, for example, to blend the polymerstogether, thereby forming an improved secondary polymer.

Extrusion

In one or more embodiments, polymer compositions in accordance with thepresent disclosure may be prepared using continuous or discontinuousextrusion. Methods may use single-, twin- or multi-screw extruders,which may be used at temperatures ranging from 100° C. to 270° C. insome embodiments, and from 140° C. to 230° C. in some embodiments. Insome embodiments, raw materials are added to an extruder, simultaneouslyor sequentially, into the main or secondary feeder in the form ofpowder, granules, flakes or dispersion in liquids as solutions,emulsions and suspensions of one or more components.

The components can be pre-dispersed in prior processes using intensivemixers, for example. Inside an extrusion equipment, the components areheated by heat exchange and/or mechanical friction, the phases are meltand the dispersion occurs by the deformation of the polymer. In someembodiments, one or more compatibilizing agents (such as afunctionalized polyolefin) between polymers of different natures may beused to facilitate and/or refine the distribution of the polymer phasesand to enable the formation of the morphology of conventional blend. Thecrosslinking agent can be added at the same extrusion stage or in aconsecutive extrusion, according to selectivity and reactivity of thesystem.

In one or more embodiments, methods of preparing polymer compositionsmay involve a single extrusion or multiple extrusions following thesequences of the blend preparation stages. Blending and extrusion alsoinvolve the selective crosslinking of the polar polymer in the dispersedphase of the polymer composition by the crosslinking agent.

Extrusion techniques in accordance with the present disclosure may alsoinvolve the preparation of a polar polymer concentrate (a masterbatch),combined with a crosslinking agent in some embodiments, that is thencombined with other components to produce a polymer composition of thepresent disclosure. In some embodiments, the morphology of a crosslinkedpolar polymer may be stabilized by crosslinking when dispersed in apolymer matrix containing polyolefins and is not dependent on subsequentprocesses for defining the morphology.

Polymer compositions prepared by extrusion may be in the form ofgranules that are applicable to different molding processes, includingprocesses selected from extrusion molding, injection molding,thermoforming, cast film extrusion, blown film extrusion, foaming,extrusion blow-molding, ISBM (Injection Stretched Blow-Molding),rotomolding, pultrusion, additive manufacturing, lamination, and thelike, to produce manufactured articles. Specifically, in one or moreembodiments, the article is an injection molded article, a thermoformedarticle, a film, a foam, a blow molded article, a 3D printed article, acompressed article, a coextruded article, a laminated article, aninjection blow molded article, a rotomolded article, an extrudedarticle, monolayer articles, multilayer articles, or a pultrudedarticle. In embodiments of a multilayer article, it is envisioned thatat least one of the layers comprises the polymer composition of thepresent disclosure.

Applications

In one or more embodiments, polymer compositions may be used in themanufacturing of articles, including rigid and flexible packaging forfood products, chemicals, household chemicals, agrochemicals, fueltanks, water and gas pipes, geomembranes, and the like.

Examples

In the following examples, a number of polymer samples are analyzed todemonstrate the changes in physical and chemical properties associatedwith polymer compositions prepared in accordance with the presentdisclosure.

Characterization Techniques

Prepared samples were characterized using a number of standardized andlab-based polymer characterization techniques discussed below.

Environmental Stress Cracking Resistance (ESCR)

For environmental stress cracking resistance tests, sample formulationswere hot pressed in 2 mm thick plaques according to ASTM D-4703, at 200°C. and under pressure. Samples were notched, bent to achieve deformationand placed in a metal U-shaped specimen holder in accordance with ASTMD-1693 procedure B, and placed in an aqueous solution containingnonylphenol ethoxylate (IGEPAL™ CO-630 from Solvay) at a percent byvolume (vol %) of 10 vol %. Failure was determined as the appearance ofany crack visible by the naked eye, in accordance with ASTM D-1693procedure B.

Flexural Modulus

The flexural modulus of the material given by the secant modulus at 1%of deformation was determined in the flexural resistance test inaccordance with ASTM D-790. The samples were previously compressionmolded in plaques in accordance with ASTM D4703.

IZOD Impact Resistance Test

The IZOD impact resistance at 23° C. of the material was determinedaccording to ASTM D-256. Samples were previously compression molded inplaques in accordance with ASTM D4703.

Definition of the Property Balance Index

Changes in physical and chemical properties of polymer compositions inaccordance with the present disclosure are characterized using an indexof properties that may be used to quantify the changes in a respectivepolymer composition based on a balance of mechanical and ESCRproperties. Improvements in a material's flexural modulus, impactresistance and ESCR may translate to better performance in variousapplications. However, improvements in a single property may be offsetby losses in other properties. In order to quantify the overallimprovement of the material, the product of the individual properties ismonitored in the examples below. The “Property Balance Index” (PBI) isdefined as shown in Eq. 1 to quantify the property changes, wherein “FM”is the flexural modulus given by the secant modulus at 1% of deformationmeasured according to ASTM D-790 in MPa, “IR” is the IZOD impactresistance at 23° C. measured according to ASTM D-256 in J/m, and “ESCR”is the environmental stress cracking resistance measured according toASTM D-1693 procedure B in hours (h).

$\begin{matrix}{{PBI} = \frac{F\; M \times {IR} \times {ESCR}}{10^{7}}} & (1)\end{matrix}$

Definition of the Normalized Property Balance Index

To compare the magnitude of property changes for different polymersystems, the PBI values were normalized according to Eq. 2, whereN_(PBI) is the normalized property balance index, PBI_(sample) is theproperty balance index obtained for the samples of this selectivereaction blend technology (reprocessed or not) and PBI_(reference) isthe property balance index obtained for the reference samples, i.e., areference polymer composition consisting of a matrix polymer compositionwithout the reprocessing.

$\begin{matrix}{N_{PBI} = \frac{{PBI}_{sample}}{{PBI}_{reference}}} & (2)\end{matrix}$

Polymer compositions in accordance with the present disclosure mayexhibit an NPBI higher than about 1.0 or higher than about one of 1.5,2.0, 3.0, 5.0 and 10. In another embodiment, polymer compositions inaccordance with the present disclosure may exhibit an N_(PBI) fallingwithin the range of 1.5 to 10 in some embodiments, and within the rangeof 3 to 9 in some embodiments. Polymer compositions in accordance withthe present disclosure may exhibit an N_(PBI) that is at least 1.5 inother embodiments. In some embodiments, the N_(PBI) value is at least1.8.

A crosslinked polymeric composition was formulated as a masterbatch (MB)composition, containing 50 wt % of polyethylene as a matrix polymer and50 wt % of selectively crosslinked PVOH (polyvinyl alcohol) based in themasterbatch composition, which was blended with virgin high densitypolyethylene (HDPE) to final contents of 5 wt % of crosslinked PVOHbased in the whole blend and processed in an extruder. Trials withdifferent polyethylene (PE) resin were performed to observe the finalproduct properties with multiple rounds of reprocessing.

The resins used in combination with the masterbatch composition (toimprove the properties of the resins) include those shown in Table 1below:

TABLE 1 Modality of High load Commercial molecular weight Melt IndexMelt Index Resin (from Co- distribution (190° C. @ (190° C. @ DensityResin Braskem) Catalyst monomer* (MWD) 2.16 kg) 21.6 kg (g/cm³) 1 HS5608Chromium 1-hexene Monomodal — 8.5 0.955 2 GF4950 Ziegler natta 1-ButeneBimodal 0.36 28 0.956 3 GF4960 Ziegler natta — Bimodal 0.34 28 0.961 4GF4950HS Ziegler natta 1-Butene Bimodal 0.21 20 0.951 5 HS5502 Chromium1-Hexene Monomodal 0.35 32 0.954 *The content of co-monomers isgenerally <1%.

The mechanical properties and yellowness index for the samples testedare shown below in Table 2.

TABLE 2 ESCR (h) Flexural Modulus IZOD impact resistance (ASTM D-1693(Mpa) at 23° C. (J/m) Sample procedure B) N_(PBI) (ASTM D-790) (ASTMD-256) Resin 2 32 1 1150 ± 18 112.0 ± 3.7 Neat Resin 2 37 1.37 1172 ± 20130.2 ± 3.2 Reprocessed 1x Resin 2 35 1.40 1189 ± 17 138.4 ± 6.5Reprocessed 2x Resin 2 12 0.45 1164 ± 19 133.1 ± 3.5 Reprocessed 3xResin 2 12 0.42 1167 ± 6 122.6 ± 2.6 Reprocessed 4x Resin 2 11 0.33 1151± 17 108.2 ± 6.0 Reprocessed 5x Resin 3 13 1 1505 ± 30 111.7 ± 4.3 NeatResin 3 17 1.76 1428 ± 37 158.7 ± 27.4 Reprocessed 1x Resin 3 14 1.531497 ± 19 159.5 ± 18.6 Reprocessed 2x Resin 3 12 1.50 1489 ± 37 183.3 ±12.6 Reprocessed 3x Resin 3 13 1.73 1461 ± 21 198.5 ± 7.1 Reprocessed 4xResin 3 13 1.58 1420 ± 34 187.5 ± 10.8 Reprocessed 5x Resin 1 258 1 1196± 16 280.8 ± 14.5 Neat Resin 1 160 0.76 1139 ± 22 362.3 ± 88.4Reprocessed 1x Resin 1 130 0.47 1147 ± 13 275.1 ± 20.3 Reprocessed 2xResin 1 120 0.53 1045 ± 16 368.2 ± 95.3 Reprocessed 3x Resin 2 with 5 wt% crosslinked 177 5.45 1229 ± 11 103.3 ± 4.0 PVOH Neat Resin 2 with 5 wt% crosslinked 173 5.48 1264 ± 11 103.2 ± 4.9 PVOH Reprocessed 1x Resin 2with 5 wt % crosslinked 112 3.54 1269 ± 18 102.8 ± 3.3 PVOH Reprocessed2x Resin 2 with 5 wt % crosslinked 155 5.29 1256 ± 22 112.0 ± 5.7 PVOHReprocessed 3x Resin 2 with 5 wt % crosslinked 117 3.88 1246 ± 11 109.6± 4.7 PVOH Reprocessed 4x Resin 2 with 5 wt % crosslinked 110 3.88 1239± 13 117.4 ± 4.4 PVOH Reprocessed 5x Resin 3 with 5 wt % crosslinked 333.14 1555 ± 11 133.6 ± 9.4 PVOH Neat Resin 3 with 5 wt % crosslinked 413.49 1535 ± 32 121.2 ± 9.0 PVOH Reprocessed 1x Resin 3 with 5 wt %crosslinked 41 3.94 1464 ± 35 143.6 ± 20.0 PVOH Reprocessed 2x Resin 3with 5 wt % crosslinked 39 4.23 1559 ± 37 151.9 ± 20.1 PVOH Reprocessed3x Resin 3 with 5 wt % crosslinked 31 3.23 1488 ± 13 153.2 ± 9.5 PVOHReprocessed 4x Resin 3 with 5 wt % crosslinked 35 3.82 1483 ± 10 160.9 ±14.3 PVOH Reprocessed 5x Resin 1 with 5 wt % crosslinked >1000 4.76*1230 ± 28 272.3 ± 32.7 PVOH Neat Resin 1 with 5 wt % crosslinked >10004.53* 1248 ± 31 314.6 ± 20.7 PVOH Reprocessed 1x Resin 1 with 5 wt %crosslinked >1000 5.48* 1265 ± 29 375.6 ± 85.7 PVOH Reprocessed 2x Resin1 with 5 wt % crosslinked >1000 4.62* 1229 ± 24 325.9 ± 62.9 PVOHReprocessed 3x Resin 1 with 5 wt % crosslinked >1000 3.95* 1205 ± 9283.7 ± 17.4 PVOH Reprocessed 4x Resin 1 with 5 wt % crosslinked >10004.84* 1212 ± 16 345.9 ± 88.0 PVOH Reprocessed 5x *For samples that theESCR values were greater than 1000 h, the N_(PBI) was calculatedconsidering the value of ESCR as 1000 h.

Overall, it can be observed that Resins 1, 2 and 3 with the addition ofthe masterbatch presented an increase in both ESCR and N_(PBI) comparedto the resins without the addition of the masterbatch composition.

It can be observed from Table 2 that Resin 1 and 2 comprising themasterbatch presented a variation after reprocessing, but maintained theESCR property more than the same resin samples without the MB for thesame reprocessing conditions. Particularly for the Resin 2 with the MB,the ESCR after reprocessing 5× decreased more or less 35% when comparedto the neat resin, while the Resin 2 without MB had the ESCR decreasedby 70% for the same number of reprocessing steps. Samples of Resin 3with or without masterbatch maintained the ESCR property as it wasreprocessed relatively stable, but the N_(PBI) value for the Resin 3with the MB was greatly increased.

The samples produced with Resin 1 without MB showed an exponentialdecrease of 55% in ESCR properties. The decrease of the ESCR propertiesfor samples of Resin 1 with MB were not able to detect as the ESCRincrease was above the commonly measured with the Standard (>1000 h).

Generally, the samples with the masterbatch exhibited a decrease in ESCRwhile maintaining a stiffness (as measured by flexural modulus) andimpact resistance level relative to the respective reference afterreprocessing. Moreover, as demonstrated, the ESCR for the polymercompositions decrease with increasing steps of reprocessing, but thatdecrease in ESCR is more notable in reference composition (without themasterbatch).

Table 3 shows the concentration of additives in the samples before andafter reprocessing.

TABLE 3 Primary and Secondary Anti-oxidants in ppm by weight Irganox ®Irgafos ® Sample I-1010 I-168 Active I-168 Degraded Resin 2 132 343 72Neat Resin 2 98 94 327 Reprocessed 1x Resin 2 50 <50 408 Reprocessed 5xResin 3 121 307 143 Neat Resin 3 77 54 401 Reprocessed 1x Resin 3 <50<50 412 Reprocessed 5x Resin 2 with 5 wt % 151 334 120 crosslinked PVOHNeat Resin 2 with 5 wt % 94 120 348 crosslinked PVOH Reprocessed 1 Resin2 with 5 wt % 74 <50 395 crosslinked PVOH Reprocessed 5x Resin 3 with 5wt % 121 369 105 crosslinked PVOH Neat Resin 3 with 5 wt % 102 299 98crosslinked PVOH Reprocessed 1x Resin 3 with 5 wt % 61 <50 352crosslinked PVOH Reprocessed 5x

Table 3 demonstrates the concentration of additives in the samples withand without masterbatch after processing. It can be noted that additivesused for the processing stabilization of polymers reacted with theproducts formed by degradation of polymers in the process therebydecreasing the amount of antioxidant presents in the polymer. Thatbehavior was similar in neat HDPE and polymers produced with crosslinkedpolymer technology. The process degradation can decrease the performanceof polymers, explaining the changes in neat polymer ESCR property.Although samples incorporating the crosslinked polymer masterbatch alsoshowed a decrease in concentration of additives after reprocessing, theydid not have drastic changes in ESCR property.

The masterbatch produced above were also blended with the polyethylene(HDPE) of Table 1 to final contents of 3 wt % of crosslinked PVOH basedin the whole blend and processed in an extruder. Trials with differentpolyethylene (PE) resin were performed to observe the final productproperties with multiple rounds of reprocessing, as presented in Table4.

TABLE 4 ESCR (h) Flexural Modulus (Mpa) SAMPLE (ASTM D-1693 procedure B)(ASTM D-790) Resin 1 Neat 180 1227 Resin 1 Reprocessed 1x 162 1337 Resin1 Reprocessed 3x 91 1270 Resin 1 Reprocessed 5x 60 1358 Resin 1 with 3wt % crosslinked PVOH Neat 700 1247 Resin 1 with 3 wt % crosslinked PVOHReprocessed 1x 510 1355 Resin 1 with 3 wt % crosslinked PVOH Reprocessed3x 480 1285 Resin 1 with 3 wt % crosslinked PVOH Reprocessed 5x 400 1359Resin 2 Neat 29 1295 Resin 2 Reprocessed 1x 40 1342 Resin 2 Reprocessed3x 24 1185 Resin 2 Reprocessed 5x 9.1 1386 Resin 2 with 3 wt %crosslinked PVOH Neat 90 1363 Resin 2 with 3 wt % crosslinked PVOHReprocessed 1x 51 1408 Resin 2 with 3 wt % crosslinked PVOH Reprocessed3x 30 1501 Resin 2 with 3 wt % crosslinked PVOH Reprocessed 5x 23 1398Resin 4 Neat 107 1062 Resin 4 Reprocessed 1x 75 1076 Resin 4 Reprocessed3x 21 1369 Resin 4 Reprocessed 5x 37 1115 Resin 4 with 3 wt %crosslinked PVOH Neat 450 1088 Resin 4 with 3 wt % crosslinked PVOHReprocessed 1x 275 1163 Resin 4 with 3 wt % crosslinked PVOH Reprocessed3x 270 1143 Resin 4 with 3 wt % crosslinked PVOH Reprocessed 5x 260 1196Resin 5 Neat 9.2 1264 Resin 5 Reprocessed 1x 6.2 1431 Resin 5Reprocessed 3x 5.5 1483 Resin 5 Reprocessed 5x 2.8 1475 Resin 5 with 3wt % crosslinked PVOH Neat 25 1388 Resin 5 with 3 wt % crosslinked PVOHReprocessed 1x 11 1445 Resin 5 with 3 wt % crosslinked PVOH Reprocessed3x 9.3 1550 Resin 5 with 3 wt % crosslinked PVOH Reprocessed 5x 8.3 1495

Although the preceding description has been described herein withreference to particular means, materials and embodiments, it is notintended to be limited to the particulars disclosed herein; rather, itextends to all functionally equivalent structures, methods and uses,such as are within the scope of the appended claims. In the claims,means-plus-function clauses are intended to cover the structuresdescribed herein as performing the recited function and not onlystructural equivalents, but also equivalent structures. Thus, although anail and a screw may not be structural equivalents in that a nailemploys a cylindrical surface to secure wooden parts together, whereas ascrew employs a helical surface, in the environment of fastening woodenparts, a nail and a screw may be equivalent structures. It is theexpress intention of the applicant not to invoke 35 U.S.C. § 112(f) forany limitations of any of the claims herein, except for those in whichthe claim expressly uses the words ‘means for’ together with anassociated function.

What is claimed is:
 1. A method, comprising: reprocessing a polymercomposition comprising a crosslinked polymeric composition, wherein thecrosslinked polymeric composition comprises a matrix polymer having apolar polymer internal phase that is selectively crosslinked with acrosslinking agent; wherein the reprocessed polymer composition retainsan environmental stress cracking resistance within 60% of the value forthe initial polymer composition when measured according to ASTM D-1693procedure B; and wherein the reprocessed polymer composition presents aNormalized Property Balance Index (N_(PBI)) greater than about 1.0,wherein the N_(PBI) is calculated according to the formula:${N_{PBI} = \frac{{PBI}_{sample}}{{PBI}_{reference}}},$  wherePBI_(Sample) is the property balance index for a sample of the polymercomposition, and PBI_(Reference) is the property balance index of areference polymer composition consisting of a matrix polymer compositionwithout the reprocessing; and wherein PBI is calculated according to theformula: ${{PBI} = \frac{F\; M \times {IR} \times {ESCR}}{10^{7}}},$ where FM is the flexural modulus of the sample as determined by secantmodulus of elasticity at 1% deformation according to ASTM D-790 in MPa,IR is the IZOD impact resistance according to ASTM D-256 in J/m, andESCR is the environmental stress cracking resistance according to ASTMD1693 procedure B in hours.
 2. The method of claim 1, whereinreprocessing comprises regrinding the crosslinked polymeric composition.3. The method of claim 1, further comprising combining the reprocessedcrosslinked polymeric composition with a secondary polymer composition.4. The method of claim 3, wherein combining the crosslinked polymericcomposition with a secondary polymer composition comprises a melt blendprocess.
 5. The method of claim 3, wherein combining the crosslinkedpolymeric composition with a secondary polymer composition comprises adry blend process.
 6. The method of claim 3, wherein the secondarypolymer composition comprises a virgin resin.
 7. The method of claim 3,wherein the secondary polymer composition comprises a post-industrialpolymer resin, a post-consumer polymer resin, a regrind polymer resinand combinations thereof.
 8. The method of claim 1, wherein the polymercomposition further comprises a secondary polymer composition that isreprocessed with the crosslinked polymeric composition.
 9. A polymercomposition, comprising: a crosslinked polymeric composition comprising:a matrix polymer comprising a polyolefin, and one or more polymerparticles dispersed in the polymer matrix, wherein the one or morepolymer particles comprise a polar polymer selectively crosslinked witha crosslinking agent, wherein the crosslinked polymer compositionretains an environmental stress cracking resistance after reprocessingthat is within 60% of the value for the initial crosslinked polymericcomposition when measured according to ASTM D-1693 procedure B.
 10. Thepolymer composition of claim 9, wherein the matrix polymer is present ina range of 30 wt % to 99.9 wt % of the crosslinked polymericcomposition.
 11. The polymer composition of claim 9, wherein the one ormore polymer particles is present in a range of 0.1 wt % to 70 wt % ofthe crosslinked polymeric composition.
 12. The polymer composition ofclaim 9, wherein the polar polymer comprises at least one functionalgroup selected from the group consisting of hydroxyl, carboxylic acid,carboxylate, ester, ether, acetate, amide, amine, epoxy, imide, imine,sulfone, phosphone and their derivatives.
 13. The polymer composition ofclaim 9, wherein the polar polymer is selected from the group consistingof polyvinyl alcohol, ethylene vinyl alcohol copolymer, ethylene vinylacetate copolymer and mixtures thereof.
 14. The polymer composition ofclaim 9, wherein the crosslinking agent is selected from the groupconsisting of maleic anhydride, maleic acid, itaconic acid, itaconicanhydride, succinic acid, succinic anhydride, succinic aldehyde, adipicacid, adipic anhydride, phthalic anhydride, pthalic acid, glutaconicacid, glutaconic anhydride, citric acid, glutaraldehyde, sodiumtetraborate, organic titanates such as tetrabutyl titanate, organiczirconates such as zirconium(IV) bis(diethyl citrato)dipropoxide,methoxy polyethylene glycol acrylates, ethoxy polyethylene glycolacrylates, ethylene glycol diacrylate, ethylene glycol dimethacrylate,polypropylene glycol diacrylate, polypropylene glycol dimethacrylate,1,3-butylene glycol diacrylate, 1,3-butylene glycol dimethacrylate,neopentyl glycol diacrylate, neopentyl glycol dimethacrylate,trimethylol ethane triacrylate, trimethylol ethane trimethacrylate,trimethylol propane triacrylate, trimethylol propane trimethacrylate,and tetramethylol methane tetracrylate, their derivatives and mixturesthereof.
 15. The polymer composition of claim 9, wherein the polymercomposition comprises one or more biobased polymers.
 16. The polymercomposition of claim 9, wherein the crosslinked polymeric compositionretains an environmental stress cracking resistance after reprocessingat least 3 times that is within 60% of the value for the initialcrosslinked polymeric composition when measured according to ASTM D1693procedure B.
 17. The polymer composition of claim 9, wherein the polymercomposition presents a Normalized Property Balance Index (N_(PBI))greater than about 1.0, wherein the N_(PBI) is calculated according tothe formula: ${N_{PBI} = \frac{{PBI}_{sample}}{{PBI}_{reference}}},$where PBI_(Sample) is the property balance index for a sample of thepolymer composition, and PBI_(Reference) is the property balance indexof a reference polymer composition consisting of a matrix polymercomposition without the reprocessing; and wherein PBI is calculatedaccording to the formula:${{PBI} = \frac{F\; M \times {IR} \times {ESCR}}{10^{7}}},$ where FMis the flexural modulus given by the secant modulus at 1% of deformationmeasured according to ASTM D-790 in MPa, “IR” is the IZOD impactresistance at 23° C. measured according to ASTM D-256 in J/m, and “ESCR”is the environmental stress cracking resistance measured according toASTM D-1693 procedure B in hours (h).
 18. The polymer composition ofclaim 9, wherein the polymer composition further comprises a secondarypolymer composition.
 19. The polymer composition of claim 18, whereinthe secondary polymer composition comprises a post-industrial polymerresin, a post-consumer polymer resin, a regrind polymer resin andcombinations thereof.
 20. The polymer composition of claim 18, whereinthe second polymer composition is a virgin polymer.
 21. A manufacturedarticle comprising the polymer composition of claim
 9. 22. Themanufactured article of claim 21, wherein the article is an injectionmolded article, a thermoformed article, a film, a foam, a blow moldedarticle, a 3D printed article, a compression molded article, acoextruded article, a laminated article, an injection blow moldedarticle, a rotomolded article, an extruded article, or a pultrudedarticle.
 23. The manufactured article of claim 22, wherein the articleis a monolayer article.
 24. The manufactured article of claim 22,wherein the article is a multilayer article and at least one of thelayers comprises the polymer composition.
 25. A method, comprising:reprocessing a polymer composition comprising a masterbatch compositionand a secondary polymer composition, wherein the masterbatch compositioncomprises a matrix polymer having a polar polymer internal phase that isselectively crosslinked with a crosslinking agent; wherein thereprocessed polymer composition retains an environmental stress crackingresistance within 60% of the value for the initial polymer compositionwhen measured according to ASTM D-1693 procedure B; and wherein thereprocessed polymer composition presents a Normalized Property BalanceIndex (N_(PBI)) greater than about 1.0, wherein the N_(PBI) iscalculated according to the formula:${N_{PBI} = \frac{{PBI}_{sample}}{{PBI}_{reference}}},$  wherePBI_(Sample) is the property balance index for a sample of the polymercomposition, and PBI_(Reference) is the property balance index of areference polymer composition consisting of a matrix polymer compositionwithout the reprocessing; and wherein PBI is calculated according to theformula: ${{PBI} = \frac{F\; M \times {IR} \times {ESCR}}{10^{7}}},$ where FM is the flexural modulus of the sample as determined by secantmodulus of elasticity at 1% deformation according to ASTM D-790 in MPa,IR is the IZOD impact resistance according to ASTM D-256 in J/m, andESCR is the environmental stress cracking resistance according to ASTMD1693 procedure B in hours.
 26. A polymer composition comprising: amasterbatch composition comprising a matrix polymer having a polarpolymer internal phase that is selectively crosslinked with acrosslinking agent; wherein the masterbatch polymer composition retainsan environmental stress cracking resistance within 60% of the value forthe initial polymer composition when measured according to ASTM D-1693procedure B; and wherein the reprocessed polymer composition presents aNormalized Property Balance Index (N_(PBI)) greater than about 1.0,wherein the N_(PBI) is calculated according to the formula:${N_{PBI} = \frac{{PBI}_{sample}}{{PBI}_{reference}}},$  wherePBI_(Sample) is the property balance index for a sample of the polymercomposition, and PBI_(Reference) is the property balance index of areference polymer composition consisting of a matrix polymer compositionwithout the reprocessing; and wherein PBI is calculated according to theformula: ${{PBI} = \frac{F\; M \times {IR} \times {ESCR}}{10^{7}}},$ where FM is the flexural modulus of the sample as determined by secantmodulus of elasticity at 1% deformation according to ASTM D-790 in MPa,IR is the IZOD impact resistance according to ASTM D-256 in J/m, andESCR is the environmental stress cracking resistance according to ASTMD1693 procedure B in hours; and a secondary polymer composition.